Computer Science 322 Operating Systems Mount Holyoke College Spring 2008

Agenda

• Announcements
  • Regular class meetings continue Friday and Monday
  • Course evaluations Monday
  • Final project presentations/demos Monday evening, 6:30, Kendade 303
• Lecture assignment recap
• RAID - a better description is on Wikipedia
• Mostly skipping: Hierarchical Storage
  • basic idea: use tapes or other large/cheap/removeable media as "swap space"
  • just another level of the memory hierarchy, really
• Protection
  • A main function of the OS: ensure that each object (hardware or software) is accessed correctly and only by those allowed access
    • memory protection
    • file protection
    • CPU protection
  • Protection domains: a set of access rights to objects
  • Processes execute in a domain, rights determined by this domain
  • Unix: domain is defined by UID and GID
    • process can change UID/GID
    • superuser (UID=0) can become any other UID/GID
    • regular users must run setuid/setgid programs
  • Other protection mechanisms are described in SG&G and we will not discuss in any detail in class
    • protection matrix
    • access control lists
    • capabilities
  • Other interesting ideas from Unix: chroot and jails

Examples

• setuid

Lecture Assignment

Our last lecture assignment.

Due at the start of class, Friday, May 2.

Turn in short answers to these questions. Please turn in a hard copy (typeset or handwritten are OK). We will discuss these questions during class, so no late submissions are accepted.

SG&G 12.8, 12.9